Digital watermarking techniques are known that may be employed in making perceptual quality of service (QoS) measurements on multimedia content in a communications network environment. For example, a known system for making perceptual QoS measurements on multimedia content in a network environment embeds reduced-reference information into the multimedia data in the form of a digital watermark. Such reduced-reference information is useful for performing in-service QoS measurements, and typically includes a limited number of characteristics of the original multimedia content such as its spectral components, variation of energy level, energy distribution in the frequency domain, and/or any other characteristic that may be sensitive to degradation during transmission of the content. Such in-service QoS measurements using reduced-reference information generally involve a comparison of the reduced-reference information obtained from the transmitted content to the reduced-reference information included in the original content to provide an objective quality metric indicating the perceived quality of the transmitted content, typically in the form of a predicted mean opinion score (MOS).
In the known system for making perceptual QoS measurements on multimedia content discussed above, a digital watermark carrying the reduced-reference information is embedded directly into the multimedia data. The multimedia content with the embedded digital watermark is then encoded, and the encoded content is transmitted over the communications network. Next, the transmitted content is received at a receiver where it is decoded. The digital watermark with the reduced-reference information is then detected and extracted from the decoded content, and a perceptual QoS measurement is performed on the transmitted content using the reduced-reference information obtained from the digital watermark.
One drawback of the above-described system for making perceptual QoS measurements on multimedia content is that the digital watermark in the multimedia data may or may not be detectable at the receiver, depending on how robust the digital watermark is to the degradation introduced during transmission of the content. For example, some digital watermark embedding techniques may produce an embedded digital watermark that is robust to limited types of degradation from sources such as image rotation, while other digital watermark embedding techniques may produce an embedded digital watermark that is robust to a broader range of degradation types from sources such as additive noise, low-pass filtering, compression and/or transmission losses, etc. If the types of degradation introduced during content transmission are such that the digital watermark embedded in the content is undetectable at the receiver, then no reduced-reference information would be available at the receiver for making perceptual QoS measurements on the transmitted content. Even if the digital watermark were detectable in the transmitted content, the reduce-reference information obtained from the detected digital watermark may be insufficient for accurately estimating the level of the degradation introduced during content transmission, thereby limiting the ability of the system to provide a useful assessment of the fidelity of the transmitted content.
Other known systems for making perceptual QoS measurements on multimedia content in a communications network environment include systems that use full-reference information and systems that use no reference information. Known perceptual QoS measurement systems that employ full-reference information typically compare the entire transmitted content to the original content to provide an objective quality metric indicating the perceived quality of the transmitted content. However, because not all of the original content is typically available at the receiver, such systems employing full-reference information are generally more suited for making out-of-service QoS measurements such as those performed in research and development settings. Known perceptual QoS measurement systems that employ no reference information generally have no access to any information about the original content, and therefore typically provide an indication of the perceived quality of the transmitted content using only the information obtained from the transmitted content. However, because such systems that use no reference information generally rely on individuals to perform subjective quality evaluations of the transmitted content, they can be inaccurate, and costly and time-consuming to implement. Moreover, like systems that use full-reference information, systems that use no reference information have traditionally been more suited for making out-of-service QoS measurements.
It would therefore be desirable to have improved systems and methods of perceptual quality assessment for multimedia content employing digital watermarking techniques that avoid one or more of the drawbacks of known systems for making perceptual QoS measurements on multimedia content.